The present invention relates to means for containing and detecting leaks in storage tanks. More particularly, the present invention relates to apparatus and methods for constructing such apparatus, for containing multiple or repeated leaks of hazardous, polluting, or otherwise undesirable fluids or solids from storage tanks, and for quickly detecting and signaling the presence of such leaks, thereby minimizing the dangers posed by storing such fluids and solids and complying with regulations requiring such containment and detection.
Storage of hazardous liquids and solids used in numerous industries requires storage tanks of all sizes. Chemical process plants, refineries, oil and gas production sites, manufacturing plants, and the like require storage of a variety of materials for processes used in such facilities. The materials so stored, whether gases, liquids, or solids, may include chemicals and compounds that could endanger the environment or pose significant health risks in the event of leakage into areas surrounding these storage systems. Heightened awareness in recent years over the quality of the environment has increased and tightened the rules, regulations, and requirements governing storage of such materials. Growing concern with public health issues has further emphasized the need to prevent leakage of hazardous materials into the environment to prevent, for leakage, contaminating drinking water or exposing humans or wildlife to hazardous compounds.
Among the regulations governing the storage discussed above, by way of example, are the rules promulgated by the Environmental Protection Agency ("EPA") for hazardous waste management systems. See, e.g., 40 C.F.R. .sctn..sctn.260-65 and .sctn.268 (1988). The EPA rules govern, among other matters, tank systems that store hazardous wastes. Id., .sctn.260.10. Hazardous wastes subject to these regulations include a host of residues, byproducts, and wastes that are generated or used in any of a lengthy list of chemical, manufacturing, and other processes. Id., .sctn..sctn.261.3-ff. Under these regulations what is designated "secondary containment" must be provided on all new tank systems storing hazardous wastes, and on existing hazardous waste systems as of various effective dates subsequent to Jan. 12, 1987. See id., .sctn.264.193 and .sctn.265.193. Such a secondary containment system must permit spilled or leaked waste to be detected in that secondary containment system within twenty-four (24) hours (or as timely as possible) after a spill or leak. Id. Furthermore, the EPA regulations deem a tank system "unfit for use" if it is no longer capable of storing or treating hazardous wastes without itself posing a threat of release of hazardous waste to the environment. Id., .sctn.260.10. Finally, the EPA regulations require that any hazardous waste materials released into a secondary containment system must be removed within twenty-four hours, or in as timely a manner as is possible. Id., .sctn.264.196. The tank system cannot be used until the released waste is removed and any necessary repairs to the system are made. (Although reference is made in the present application to EPA regulations and the definitions used in those regulations, those definitions are not intended to, and do not, generally govern the use of terms in this application. Except as may be expressly noted to the contrary, all terms used in this application are to have their common and accepted means.)
Therefore, an acceptable secondary containment system under these EPA regulations must, in general terms, be capable of collecting and accumulating liquids that leak from a tank, detecting such a leak or the presence of the accumulated liquids in the system, and permitting removal of such liquids, all within twenty-four (24) hours of the leak. Id. As can be seen, therefore, the EPA regulations, as well as increasing safety and health concerns, have imposed stringent requirements for containing, detecting, and removing leakage of hazardous materials from storage tank systems. Effective, economical, and safe double containment and leak detection systems, therefore, are not only desirable but also mandatory, both for new and existing tank systems.
The cost of building new systems or converting old systems to comply with the EPA regulations could be astronomical if not performed with a minimum of alteration to tank systems built under previous requirements. Prior attempts at meeting the EPA regulations have encountered problems and proven unsatisfactory, for a variety of reasons. For example, various plastic liners, both internal and external, have been used in trying to meet the secondary containment requirement of the EPA regulations. Such liners, however, have split at their seams and would lead to contamination of the soil in the event of external tank leaks. Since liner systems do not form a sealed containment space, it is virtually impossible to inspect or test the integrity of the liner systems. To meet the requirements for removal of wastes, the contaminated soil then has to be removed and disposed of, which requires either removing the tank bottom or lifting the entire tank, to permit digging up the soil. This process of lifting or dismantling the tank and removing soil (which generally needs to be replaced) is very expensive and time-consuming. Another unsuccessful attempt to meet the EPA secondary containment regulations has utilized double-walled and double-bottom tanks, generally made of steel, with the annular space between the walls and bottoms filled with sand or other filler material. This latter technique has also proven to be unacceptable, because it fails to allow for removing, cleaning, and disposing the filler material should a leak occur.
It can be seen, therefore, that a need exists for meeting EPA regulations and satisfying environmental and safety concerns in general by providing economical, effective, and reliable double containment and leak detection system for storage tanks, for both new and existing storage tanks.
U.S. Pat. No. 4,939,833, issued on Jul. 10, 1990, to the present inventor, describes such a double containment and leak detection system. In this invention, a plurality of baffle supports are provided so as to maintain a baffle plate in a proper position above the tank bottom. These baffle supports are disposed in a generally parallel fashion on the upper surface of the tank bottom. Each baffle support is placed on the upper surface of the tank bottom with the opposite ends of each baffle support located adjacent to points on the interior periphery of the shell. It was indicated in this patent that it could be readily seen by those skilled in the art that a variety of techniques and materials could be used to provide adequate structural support for the baffle plate so long as the baffle plate is supported sufficiently to bear the weight of the materials to be stored within the tank body without undue or impermissible stress or deflection. After experimentation, it was found that, for large tanks, a large number of the steel structural members would be required to provide the necessary structural support. It was found that, although these provide a superior support for the baffle plate, it was relatively costly. As such, it was felt to be important to accommodate the needs of secondary containment and leak detection in low cost applications.
It is an object of the present invention to provide a baffle plate support system that is inexpensive and easy to utilize.
It is another object of the present invention to provide a baffle plate support system that is compatible with leak detection.
It is still a further object of the present invention to provide a leak detection system that can be used in the containment space between the baffle plate and the tank bottom.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.